508 MR. BROAD IN REPLY TO MR. FLEMING. 
are flat and weak which sort of shoes the horse travels best 
in, and it may also soon be seen which preserve the feet in 
the soundest state; but to understand the theory of the 
same does require a knowledge of the laws of mechanics. 
Having ascertained the fact from practical experience that 
horses^ feet receive less concussion when travelling on hard 
roads or paved streets, when shod with heavy shoes, than 
when shod with light ones, the mechanical law showing the 
theorv of the same is that of vibration, the result of con- 
4/ 
cussion—the lighter the body, the greater the vibration, pro¬ 
vided that the blows causing the concussion are equal. When 
the light shoe comes in contact with the pitching, a large 
amount of vibration is produced, and received by the foot; 
but in proportion as the shoe is increased in weight the 
vibration decreases in quantity. The shoe being brought 
into contact with the pitching by voluntary muscular power, 
the concussion is not increased by the extra weight of shoe, 
in proportion to the decrease of vibration resulting from the 
same. 
It is a well known fact that the effect of constant vibra¬ 
tion on iron produces molecular alteration of structure ; that 
which was of the best fibrous quality becomes crystallized and 
easily fractured. Therefore we need not be surprised at the 
effect it produces on the functions and structure of the foot 
of the horse. The rationale of the heavy and peculiarly made 
bar-shoes, as used in laminitis, is that, in addition to the 
lessening of vibration, they allow the horse to throw his 
weight on to the heels and frogs, thereby relieving the 
lamina more effectually than he can do with light shoes, or 
without any. I state this after having fully tested both plans, 
and, were it not for occupying too much space, I could cite 
a number of cases in proof of it. However, I will give the 
history of two. The letters corroborative of the first case 
have been seen by several members, including Mr. Fleming. 
The second case occurred during the time my friend Mr. 
AYoodger, sen., was paying me a visit, so that he can corrobo¬ 
rate me in that case. In October last I went a distance of 
fifteen miles, to oblige a veterinary surgeon (without fee or 
expenses), to instruct him in my plan of treating a case of 
laminitis in both fore feet of a favorite pony, the property of 
a nobleman. The cause of the disease was fat, and idleness 
when at grass. The case had then been under treatment two 
months, and the pony moved with difficulty. I lent the 
veterinary surgeon a pattern shoe, also instructed the smith 
how to make new ones, ordered physic and exercise, at the 
same time stating that if those instructions were properly 
